Multilayered substrate for semiconductor device

ABSTRACT

A multilayered substrate for a semiconductor device, which has a multilayered substrate body formed of a plurality sets of a conductor layer and an insulation layer, and having a face for mounting a semiconductor element thereon and another face for external connection terminals, the face for mounting a semiconductor device being provided with pads through which the substrate is connected to a semiconductor element to be mounted thereon, and the face for external connection terminals being provided with pads through which the substrate is connected to an external electrical circuit, wherein a reinforcing sheet is respectively joined to the face for mounting a semiconductor element thereon and the face for external connection terminals of the multilayered substrate body.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a multilayered substrate for asemiconductor device, and more particularly, to a multilayered substratefor a semiconductor device, which has a multilayered substrate bodyformed of a plurality of sets of a conductor layer and an insulationlayer, i.e., a laminate of alternate conductor and insulation layers,and having a face for mounting semiconductor element thereon and anotherface for external connection terminals, the face for mountingsemiconductor device being provided with pads through which thesubstrate is connected to a semiconductor element to be mounted thereon,and the face for external connection terminals being provided with padsthrough which the substrate is connected to an external electricalcircuit.

2. Description of the Related Art

A multilayered substrate for a semiconductor device as shown in FIG. 10is proposed in Japanese Unexamined Patent Publication No. 2000-323613(corresponding to U.S. Pat. No. 6,418,615). Multilayered substrate body105 is included in multilayered substrate 100 for a semiconductor deviceshown in FIG. 10 that is composed by arranging conductor wiring 102 inmultiple layers stacked with insulation layers 104 composed of apolyimide resin or a resin such as polyphenylene ether. One side of thismultilayered substrate body 105 is a face for mounting semiconductorelements on which is formed semiconductor element pads 120 a that areconnected to electrode terminals 108 of semiconductor element 106 thatis mounted thereon, while the other side of multilayered substrate body105 is a face for external connection terminals on which is formedexternal connection terminal pads 124 that are attached to solder balls122 as external connection terminals. The face for mountingsemiconductor devices and the face for external connection terminals ofthis multilayered substrate body 105 are covered with solder resist 126with the exception of semiconductor element pads 120 a and externalconnection terminal pads 124.

In this type of multilayered substrate body 105, the conductor wiring102 and/or pads formed on both sides of each insulation layer 104 (pads120 for connecting two wiring layers to each other, pads 124 forexternal connection terminals or pads 120 a for electrode terminals ofsemiconductor element) are electrically connected by vias 128 formedpassing through insulation layers 104. These vias 128 are formed inopenings 130 which are opened in the side of insulation layer 104 havingthe face for external connection terminals, and have the bottom formedby the faces of conductor wiring 102 or pads 120 and 120 a formed on theside of the same insulation layer 104 having the face for mountingsemiconductor elements. Moreover, a metal frame 117 having a prescribedstrength can be joined to the periphery of multilayered substrate body105 in order to improve handling ease, etc. during transport and soforth of multilayered substrate 100 for a semiconductor device.

As shown in FIGS. 11A through 11F, multilayered substrate 100 for asemiconductor device shown in FIG. 10 can be produced by alternatelyforming conductor wiring and insulation layers from a semiconductorelement mounting layer having a face for mounting semiconductor elementsin the direction of an external connection terminal attachment layerhaving a face for external connection terminals.

To begin with, seed layer 142 is formed on one side of a metal sheet inthe form of copper sheet 140 (FIG. 11A). This seed layer 142 is composedof chromium (Cr) layer 141 a, which is in direct contact with the faceof copper sheet 140, and copper (Cu) layer 141 b formed on chromium (Cr)layer 141 a as shown in FIGS. 12, which is an enlarged view of thesection indicated with circle A in FIG. 11A.

Semiconductor element pads 120 a, to which electrode terminals 108 ofsemiconductor element 106 are later connected and which are composed ofcopper, are formed by forming a photoresist pattern (not shown) on seedlayer 142 formed on one side of copper sheet 140, exposing seed layer142 at the sections where semiconductor element pads 120 a are formed,and then performing electrolytic plating using seed layer 142, andparticularly copper layer 141 b, as the power supply layer (FIG. 11B).

Insulation layer 104 is formed by coating a thermosetting resin in theform of a polyimide resin by printing and so forth followed by curing soas to cover semiconductor element pads 120 a formed in this manner (FIG.1C). Continuing, openings 130 for forming vias are formed in insulationlayer 104 by laser light such as YAG laser light or carbon dioxide laserlight (FIG. 1D).

Seed layer 142′, composed of a chromium (Cr) layer and copper (Cu)layer, is formed over the entire surface of insulation layer 104,including the inner walls of formed openings 130 (FIG. 11E). Next,sections corresponding to vias 128 and conductor wiring 102 (FIG. 10)are formed by electrolytic copper plating using the resist pattern (notshown) formed on seed layer 142′ as a mask, and seed layer 142′ as apower supply layer.

Next, vias 128 and conductor wiring 102 are formed in the surface ofinsulation layer 104 as shown in FIG. 11F by removing seed layer 142′,except for those sections corresponding to vias 128 and conductor wiring102, by etching.

Continuing, conductor wiring and insulation layers are sequentiallyformed from the side of the semiconductor element mounting layer havinga face for mounting semiconductor elements in the direction of theexternal connection terminal attachment layer having a face for externalconnection terminals by repeating the steps of FIGS. 11C through 11F,thereby allowing the obtaining of intermediate 100 a shown in FIG. 13.On one side of multilayered substrate body 105 of the resultingintermediate 100 a, copper sheet 140 is joined via seed layer 142 to theface for mounting semiconductor element on which semiconductor mountingpads 120 a are formed, and on the other side of multilayered substratebody 105, external connection terminal pads 124 are formed. Copper sheet140 fulfills the role of a reinforcing sheet of multilayered substratebody 105, and facilitates handling of intermediate 100 a duringtransport and so forth.

Finally, it is necessary to remove copper sheet 140 from intermediate100 a by etching in order to obtain multilayered substrate 100 for asemiconductor device shown in FIG. 10. By forming chromium (Cr) layer141 a, which is not etched by the etching solution of copper sheet 140,as a portion of seed layer 142, the progress of the etching can beinhibited when etching has reached chromium (Cr) layer 141 a of seedlayer 142 during etching of copper sheet 140, and etching of coppersheet 140 ends at the point the entire surface of chromium (Cr) layer141 a of seed layer 142 is exposed. Next, by removing chromium (Cr)layer 141 a and copper (Cu) layer 141 b by etching, the surface ofsemiconductor element pads 120 a is exposed, thereby allowing theobtaining of multilayered substrate 100 for a semiconductor device shownin FIG. 10.

Multilayered substrate 100 for a semiconductor device shown in FIG. 10can be produced so that the face on which semiconductor elements aremounted is as flat as possible and the thickness of the substrate is asthin as possible. However, the inventors of the present invention foundthat, even if multilayered substrate 100 for a semiconductor deviceshown in FIG. 10 is reinforced by joining a metal frame 117 on the facefor mounting semiconductor elements of multilayered substrate body 105,warping occurs easily caused by a difference in the coefficients ofthermal expansion between metal frame 117 and multilayered substratebody 105 composed mainly of a resin, and that warping also occurs easilyin intermediate 10 a (FIG. 13) during its production process caused by adifference in the coefficients of thermal expansion between copper sheet140 and multilayered substrate body 105 composed mainly of a resin.

If a thick metal frame 117 is used to prevent the occurrence of thiswarping, the characteristics of a thin and lightweight multilayeredsubstrate 100 for a semiconductor device are lost.

SUMMARY OF THE INVENTION

The object of the present invention is to provide a multilayeredsubstrate for a semiconductor device in which the face on whichsemiconductor elements are mounted can be as flat as possible and itsthickness can be as thin as possible, and which can prevent warpingcaused by a difference in the coefficients of thermal expansion betweenthe element members.

In order to achieve the above object, the present inventors thought thatit would be effective to juxtaposition a multilayered substrate bodycomposed mainly of resin between a metal frame and a metal sheet, and asa result of conducting studies on this, were able to achieve the presentinvention.

The present invention is a multilayered substrate for a semiconductordevice, which has a multilayered substrate body formed of a plurality ofsets of a conductor layer and an insulation layer, i.e., a laminate ofalternate conductor and insulation layers, and having a face formounting semiconductor element thereon and another face for externalconnection terminals, the face for mounting semiconductor device beingprovided with pads through which the substrate is connected to asemiconductor element to be mounted thereon, and the face for externalconnection terminals being provided with pads through which thesubstrate is connected to an external electrical circuit, wherein areinforcing sheet is respectively joined to the face for externalconnection terminals and the face for mounting semiconductor elementthereon.

A metal sheet having through holes formed so as to correspond to eachexternal connection terminal pad, and the entire surface of which,including the inner wall surfaces of these through holes, has beeninsulation treated, is preferable for the reinforcing sheet joined tothe face for external connection terminals. In particular, an aluminumsheet in which a plurality of through holes are formed, and the entiresurface of which, including the inner wall surfaces of each of the abovethrough holes, is anodized can be used preferably.

As the reinforcing sheet joined to the face for external connectionterminals, a sheet of ceramic or resin, which has a strength and acoefficient of thermal expansion corresponding to those of thereinforcing sheet jointed to the face for mounting semiconductorelements, may be used.

When adhering said insulation treated metal sheet to the face forexternal connection terminals of the multilayered substrate body, byusing an adhesive containing particles of a diameter that is able tomaintain a prescribed gap between the above insulation treated metalsheet and face for external connection terminals such that adhesive isnot extruded into the through holes of the above insulation treatedmetal sheet when the insulation treated metal sheet and face forexternal connection terminals are pressed together, attachment ofexternal connection terminals can be carried out easily.

A metal frame is preferable for the reinforcing sheet joined to the facefor mounting semiconductor elements. In particular, a portion of a metalsheet on which a multilayered substrate body is formed on one side canbe used as such a frame, whereby the occurrence of warping of themultilayered substrate for a semiconductor device in the productionprocess can be prevented. In this case, a frame that functions as areinforcing sheet can be formed by etching a metal sheet on which amultilayered substrate body is formed on one side and removing only themetal material in the region where a semiconductor element is mounted.

In the multilayered substrate for a semiconductor device of the presentinvention, pads formed into the shape of bumps so that their tipsprotrude from the face for mounting a semiconductor element of themultilayered substrate body may be used as the pads for mountingsemiconductor elements on the multilayered substrate. As a result ofusing such bump-shaped pads, even a semiconductor element provided withelectrode terminals having flat tips can be easily joined to themultilayered substrate of the present invention by means of thesebump-shaped pads.

According to the present invention, a multilayered substrate body inwhich a plurality of conductor wiring are formed in multiple layers withinsulation layers between them allows the face on which semiconductorelements are mounted to be made as flat as possible, and its thicknesscan be made to be as thin as possible.

Moreover, since a multilayered substrate body composed mainly ofinsulating resin is juxtapositioned between an insulation treated metalsheet and metal frame, the multilayered substrate for a semiconductordevice can be prevented from warping, even if there is a difference inthe coefficients of thermal expansion between the multilayered substratebody and these metal members.

Moreover, since a multilayered substrate body is juxtapositioned betweenan insulation treated metal sheet and metal frame having rigidity,handling of a multilayered substrate for a semiconductor device can bemade to be easier during transport and so forth.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other objects and advantages of the invention will be wellunderstood and appreciated by a person with ordinary skill in the art,from consideration of the following detailed description made byreferring to the attached drawings, wherein:

FIG. 1 is a partial cross-sectional view that illustrates an embodimentof the multilayered substrate for a semiconductor device according tothe present invention,

FIG. 2 is a top view of the frame shown in FIG. 1,

FIG. 3 is an enlarged, partial cross-sectional view of the insulationtreated metal sheet shown in FIG. 1,

FIGS. 4A through 4G illustrate an example of the production method ofthe multilayered substrate for a semiconductor device shown in FIG. 1,

FIG. 5 illustrates the metal sheet used in the production method shownin FIGS. 4A through 4G,

FIG. 6A illustrates the insulation treated metal sheet used in theproduction method shown in FIGS. 4A through 4G,

FIG. 6B is a cross-sectional view taken along the line B-B in FIG. 6A,

FIG. 7 is an enlarged, partial cross-sectional view of the vicinity of athrough hole of the insulation treated metal sheet shown in FIGS. 6A and6 b,

FIGS. 8A through 8D illustrate another example of a production method ofthe multilayered substrate for a semiconductor device shown in FIG. 1,

FIGS. 9A and 9B show another example of a reinforcing material joined toa face for external connection terminals of the multilayered substratefor a semiconductor device of the present invention,

FIG. 10 is a partial cross-sectional view of a multilayered substratefor a semiconductor device of the prior art,

FIGS. 11A through 11F illustrate a production method of a multilayeredsubstrate for a semiconductor device of the prior art,

FIG. 12 is a partially enlarged section of the portion, indicated bycircle A, of the copper sheet of FIG. 11A, showing construction of aseed layer provided on its surface, and

FIG. 13 is a partial cross-sectional view of an intermediate obtained inthe production method of a multilayered substrate for a semiconductordevice shown in FIG. 11.

DETAILED DESCRIPTION OF THE INVENTION

An example of the multilayered substrate for a semiconductor device ofthe present invention is shown in FIG. 1. In multilayered substrate 50for a semiconductor device shown in FIG. 1, multilayered substrate body20, which is composed by conductor wiring 26 being formed in multiplelayers via insulating resin layers 20 a, is juxtapositioned betweencopper frame 10, having a surface on which nickel film 12 is formed, andinsulation treated metal sheet 30. This copper frame 10 and insulationtreated metal sheet 30 have the role of a reinforcing material formultilayered substrate body 20.

Copper frame 10 is joined to the face for mounting semiconductorelements of multilayered substrate body 20, on which is formed solderlayer 24 serving as semiconductor element pads that are connected withthe electrode terminals of semiconductor element 39. As shown in FIG. 2,opening 18 is formed in the center of frame 10 so as to allow theinsertion of semiconductor element 39.

As shown in FIG. 1, each of the electrode terminals of semiconductorelement 39 inserted into opening 18 of frame 10 is joined to solderlayer 24 serving as semiconductor element pads formed on the face formounting semiconductor elements of multilayered substrate body 20.

Insulation treated metal sheet 30 is adhered to the face for externalconnection terminals, on which external connection terminal pads 33 areformed, of multilayered substrate body 20. As shown in FIG. 3, thisinsulation treated metal sheet 30 is formed from metal sheet 34, inwhich through holes 28 are provided by which solder balls 38 (FIG. 1)serving as external connection terminals are attached to externalconnection terminal pads 33, and insulating film 36 that covers itsentire surface, including the inner wall surfaces of through holes 28.An aluminum sheet is preferably used for metal sheet 34, and an alumite(Al₂O₃) layer can be formed for insulating film 36. Metal sheets otherthan an aluminum sheet can also be used. For example, a sheet of anymetal material in which an insulating resin film is formed on the entiresurface, including the inner wall surfaces of through holes 28, can beused.

Adhesion of insulation treated metal sheet 30 and multilayered substratebody 20 is carried out by adhesive 32 containing insulating fineparticles 37. Insulating fine particles 37 blended into adhesive 32prevent adhesive 32 from being extruded into through holes 28 bymaintaining a prescribed gap between insulation treated metal sheet 30and insulating resin layer 20 a even if insulation treated metal sheet30 is pressed against multilayered substrate body 20 for the purpose ofadhesion when insulation treated metal sheet 30 is adhered to insulatingresin film 20 a of the outermost layer of multilayered substrate body20. Thus, the diameter of insulating fine particles 37 is selected so asto be able to maintain a gap that makes it possible to prevent extrusionof adhesive 32 into through holes 28 between insulation treated metalsheet 30 and multilayered substrate body 20. An adhesive that does notcontain insulating fine particles 37 can also be used by experimentallyconfirming the gap that makes it possible to prevent extrusion ofadhesive 32 into through holes 28, and then adjusting the pressing forceduring adhesion accordingly.

The multilayered substrate 50 for a semiconductor device shown in FIG. 1can be produced in the manner described below.

To begin with, on two exposed surfaces of a compound metal sheet inwhich two metal sheets are laminated into a single unit, a patternedsolder layer (wiring layer), which is made from a metal that issubstantially not etched by an etching liquid for the metal sheets, andpatterned insulating layer 20 a are formed. This patterned solder layerprovides semiconductor element pads 24 on the face for mounting asemiconductor element of the multilayered substrate. Insulating layer 20a is patterned so as to have openings that expose at least a portion ofeach pad 24. A wiring layer connected to pads 24 through the openings ofthis insulating layer is formed, and an insulating layer is formedhaving openings leading to the newly formed wiring layer. Afterrepeating alternate formation of the wiring layer and insulating layerfor the required number of times (external connection terminal pads 33are provided through the formation of the final wiring layer), thecompound metal sheet is separated to obtain an intermediate in whichmultilayered substrate body 20 is formed on one side of one metal sheet.The metal material in the region where a semiconductor element ismounted is removed from the metal sheet of this intermediate, andtogether with exposing semiconductor element pads, a frame is formedthat is joined to the face for mounting a semiconductor element of themultilayered substrate body, followed by adhering an insulation treatedmetal sheet to the face for external connection terminals of themultilayered substrate body to obtain multilayered substrate 50 for asemiconductor device shown in FIG. 1.

Next, a detailed explanation is provided of the production method ofmultilayered substrate 50 for a semiconductor device shown in FIG. 1with reference to the drawings.

To begin with, a copper sheet 11 having a thickness of about 0.3 mm isused for the metal sheet, and nickel film 12 is formed on one side. Thisnickel film 12 is a metal film that is resistant to etching liquid thatetches copper sheet 11. Nickel film 12 can be formed by plating orsputtering and so forth. Two copper sheets 11, on which nickel film 12is formed on one side in this manner, are laminated so that nickel film12 is on the inside to integrate into a single unit and form compoundmetal sheet 14 (FIG. 4A). As shown in FIG. 5, compound metal sheet 14 isformed by adhering the vicinity of the edges of copper sheets 11 (regionextending from the edge to broken line 16) with adhesive to integrateinto a single unit. This compound metal sheet 14 can be easily separatedinto individual copper sheets 11 as will be explained later by cuttingalong broken line 19 in the vicinity of the inside of the region adheredwith adhesive.

As shown in FIG. 4B, a thermosetting resin or photosensitive resin suchas polyimide resin or epoxy resin is applied to both sides of compoundmetal sheet 14 by printing and so forth and then cured to forminsulating resin layer 20 a. Openings 22 for forming vias are formed ininsulating resin layer 20 a by laser light such as YAG laser light orcarbon dioxide laser light, or by photolithography. Solder layer 24 isformed on the bottom of openings 22 by electrolytic plating using coppersheet 11, a portion of which is exposed on the bottom of each opening22, as a power supply layer. Alternatively, after forming solder layer24 for use as a semiconductor element connecting pad on copper sheet 11,insulating resin layer 20 a may be formed followed by forming openings22, in which solder layer 24 is exposed on the bottom, in insulatingresin layer 20 a by laser light or photolithography. Solder layer 24 isa layer that is composed of a metal that is substantially not etched byetching liquid for performing etching on copper sheet 11, and providessemiconductor element pads. Insulating resin layer 20 a may be formed byadhering a film composed of a resin such as polyimide resin or epoxyresin.

Next, multilayered substrate body 20 is fabricated by alternatelyforming conducting wiring layer 26 and insulating resin layer 20 a onboth sides of compound metal sheet 14 using a known method (FIG. 4C).

Formation of conducting wiring layer 26 can be carried out by, forexample, forming a copper layer on previously formed insulating layer 20a that is continuous with lower wiring layer 26 through openings 22formed in this insulating layer 20 a by, for example, plating orsputtering, forming a resist pattern on this copper layer, performingelectrolytic plating by using this resist pattern as a mask and usingthe copper layer as a power supply layer, forming conductor wiringlayers 26 that contain via holes, and then removing the copper layerother than the portions corresponding to conductor wiring layers 26,including vias, by etching. Formation of insulating resin layer 20 a canbe carried out by, for example, forming an insulating resin filmcomposed of a thermosetting resin such as polyimide resin or epoxy resinon the formed conducting wiring layer 26, and forming openings 22 forthe formation of vias in this insulating resin film by YAG laser lightand so forth.

Insulation treated metal sheet 30 is adhered using adhesive (not shown)on the wiring layer 26 including external connection terminal pads 33 ofthe outermost layer of each multilayered substrate body 20 formed onboth sides of compound metal sheet 14 (FIG. 4D). This insulation treatedmetal sheet 30 composes the outermost insulating layer at the face forexternal connection terminals of multilayered substrate body 20. Asshown in FIG. 6A, insulation treated metal sheet 30 has through holes 28at locations corresponding to external connection terminal pads 33, andits entire surface, including the inside wall surfaces of through holes28, is covered with an insulating film (not shown). Moreover, as shownin FIG. 6B, an adhesive 32 is pre-coated onto the side of insulationtreated metal sheet 30 that joins to multilayered substrate body 20.

FIG. 7 shows an enlarged, partial cross-sectional view of the vicinityof a through hole 28 of insulation treated metal sheet 30. Insulatinglayer 36 is formed over the entire surface of this metal sheet 30,including the inner wall surfaces of through hole 28. In the case wheremetal sheet 30 is made of aluminum, insulating layer 36 may be analumite (Al₂O₃) layer obtained by anodic oxidation, or may be a layer ofinsulating resin. An adhesive 32 containing insulating fine particles 37of a prescribed diameter is coated onto one side of insulation treatedmetal sheet 30 as was previously explained.

When multilayered substrate body 20 is formed on both sides of compoundmetal sheet 14 in this manner, the strength of compound metal sheet 14is improved as compared with the case of forming multilayered substratebody 20 on one side of a single copper sheet 11, and even if there is adifference in the coefficients of thermal expansion between copper sheet11 and multilayered substrate body 20 composed mainly of resin, sincethe directions of warping due to a difference in the coefficients ofthermal expansion between copper sheet 11 and multilayered substratebody 20 are mutually opposite on both sides of compound metal sheet 14,the warping that occurs on each side of compound metal sheet 14 can becanceled out. Thus, in the steps explained with reference to FIGS. 4Athrough 4D, there is no substantial occurrence of warping in compoundmetal sheet 14 or multilayered substrate body 20, and positioning can becarried out both reliably and easily when forming openings for formationof vias in insulating resin layer 20 a by YAG laser light and so forth,and when adhering insulation treated metal sheet 30.

Following adhesion of insulation treated metal sheet 30, an intermediate34, in which multilayered substrate body 20 is formed on one side of asingle copper sheet 11, can be obtained by separating two copper sheets11 composing compound metal sheet 14 on which multilayered substratebody 20 is formed on both sides, as shown in FIG. 4E. As shown in FIG.5, separation of the two copper sheets 11 can be carried out easily bycutting compound metal sheet 14 along a line (for example, broken line19 in FIG. 5) on the inside of their edge regions (regions extendingfrom the edge of copper sheet 11 to broken line 16) that have beenlaminated with adhesive.

Intermediate 34 obtained in this manner (FIG. 4E) is able to prevent theoccurrence of warping even if heat is applied due to multilayeredsubstrate body 20 made mainly of resin being juxtapositioned betweencopper sheet 11 and insulation treated metal sheet 30.

As shown in FIG. 4F, nickel film 12 of intermediate 34 is patterned, andthe section corresponding to opening 18 (FIG. 1) for arranging asemiconductor element is removed to expose the central portion of coppersheet 11. Continuing, the exposed portion of copper sheet 11 is removedby etching by using the remaining nickel film 12 as a mask, allowing theobtaining of multilayered substrate 50 for a semiconductor device inwhich copper frame 10 is joined to the face for mounting a semiconductorelement of multilayered substrate body 20 as shown in FIG. 4G. Duringetching of copper sheet 11, a mask sheet is attached to the face forexternal connection terminals on which external connection terminal padsof multilayered substrate body 20 are formed. An etching liquid thatetches copper sheet 11 but does not etch solder layers 24 is used forthe etching liquid for copper sheet 11.

In multilayered substrate 50 for a semiconductor device fabricated inthis manner, copper frame 10 acts as a reinforcing sheet formultilayered substrate 50 for a semiconductor device together withinsulation treated metal sheet 30, and is thus able to improve thestrength of the substrate. In particular, since multilayered substrate50 for a semiconductor device obtained with the production method shownin FIGS. 4A through 4G has multilayered substrate body 20, composedmainly from resin, juxtapositioned between frame-shaped copper sheet 10and insulation treated metal sheet 30, its strength can be furtherimproved. Moreover, warping of multilayered substrate 50 can beeffectively prevented, and handling during transport and so forth can befacilitated.

In addition, according to the multilayered substrate 50 for asemiconductor device (FIG. 1), since conductor wiring 26 of multilayeredsubstrate body 20 are formed by a method in which they are formed inmultiple layers between insulating resin layers 20 a from one side ofcopper sheet 11, the face on which semiconductor element 39 is mountedcan be formed as flat as possible, and its thickness can be formed asthin as possible in comparison with a multilayered substrate produced bya method in which a core substrate is used and multilayered conductorwiring layers are formed on both sides of the core substrate.

Multilayered substrate 50 for a semiconductor device is able to providea packaged semiconductor device by attaching external connectionterminals in the form of solder balls 38 to external connection terminalpads 33, and contacting electrode terminals 40 of a semiconductorelement 39 to solder layers 24 formed as semiconductor element pads,followed by reflowing the solder.

In the production method of a multilayered substrate for a semiconductordevice as previously explained, although a compound metal sheet 14 wasused in which two copper sheets 11, on which a metal film in the form ofnickel film 12 is formed on one side, are laminated into a singlestructure so that the nickel films 12 are on the inside, a compoundmetal sheet may also be used in which two copper sheets are integratedinto a single structure without forming nickel films. In this case,during removal of the portion corresponding to opening 18 (FIG. 1) forarranging a semiconductor element of the copper sheet that composes theintermediate, it is necessary to perform etching by forming an etchingresist film or placing a mask sheet at the portion of copper sheet 11that is not to be etched.

After forming openings 22 (FIG. 4B) for forming vias in insulating resinlayers 20 a formed on both sides of compound metal sheet 14, etching orlaser processing may be performed on the portions of copper sheet 11exposed in the bottoms of the openings 22 formed in insulating resinlayer 20 a to provide recesses 22′ in which the bottoms are formed incopper sheet 11 passing through insulating resin layer 20 a, as shown inFIG. 8A. After forming solder layer 24 for semiconductor elementmounting pads by electrolytic plating of the bottoms of these recesses22′ using copper sheet 11 as the power supply layer, as shown in FIG.8B, conductor wiring layers 26 are formed by a known method (FIG. 8C).

In a multilayered substrate 50, for a semiconductor device fabricatedwith this method, semiconductor element connection pads 24′ can beformed in the shape of bumps protruding from the surface of theoutermost insulating resin layer 20 a, as shown in FIG. 8D. The use ofsuch a multilayered substrate for a semiconductor device in which thesebump-shaped semiconductor element pads 24′ are formed enables asemiconductor element 39′ to be easily and directly joined to themultilayered substrate of the present invention by means of thesebump-shaped pads 24′ even if the semiconductor element 39, is providedwith electrode terminals 40′ having flat tips.

In the multilayered substrate for a semiconductor device as explainedabove, insulation treated metal sheet 30, on which insulation treatmenthas been performed over the entire surface, including the inner wallsurfaces of through holes 28 formed so as to correspond to each ofexternal connection terminal pads 33, is joined to the face for externalconnection terminals as a reinforcing material as shown in FIG. 1. Ametal frame 45 similar to that joined to the face for mounting asemiconductor element, as shown in FIG. 9A, or a frame 45′ provided withcords in the form of band-shaped reinforcing members 47, as shown inFIG. 9B, may be used for the reinforcing material for the multilayeredsubstrate for a semiconductor device. These frames 45 and 45′ may befabricated from a metal material that has not undergone insulationtreatment of its surface provided they do not come in direct contactwith external connection terminal pads 33. When these frames 45 and 45′are joined to the face for external connection terminals of multilayeredsubstrate body 20, a plurality of external connection terminal pads 33are located in the openings of frames 45 and 45′.

The vias of the multilayered substrate for a semiconductor device 50(FIG. 1) of the present invention may be formed by filling a metal intoopenings 22 of insulating resin layers 20 a (FIG. 4B) by plating. Inaddition, a plurality of multilayered substrate bodies 20 may be formedon a single copper sheet 11 used as a metal sheet, and a plurality ofmultilayered substrates 50 for a semiconductor device may be formed allat once.

As has been explained above, according to the present invention, a thinand lightweight multilayered substrate for a semiconductor device can beused without the occurrence of warping and having improved reliability.Moreover, the strength of the multilayered substrate for a semiconductordevice of the present invention can be improved, enabling it tofacilitate handling during transport and so forth.

1. A multilayered substrate for a semiconductor device, which has amultilayered substrate body formed of a plurality sets of a conductorlayer and an insulation layer, and having a face for mounting asemiconductor element thereon and another face for external connectionterminals, the face for mounting a semiconductor device being providedwith pads through which the substrate is connected to a semiconductorelement to be mounted thereon, and the face for external connectionterminals being provided with pads through which the substrate isconnected to an external electrical circuit, wherein a reinforcing sheetis respectively joined to the face for mounting a semiconductor elementthereon and the face for external connection terminals of themultilayered substrate body.
 2. The multilayered substrate for asemiconductor device of claim 1, wherein the reinforcing sheet joined tothe face for external connection terminals has through holescorresponding to the respective pads for the external connectionterminals.
 3. The multilayered substrate for a semiconductor device ofclaim 2, wherein the reinforcing sheet is made of a metal, and theentire surface thereof, including the inner wall surfaces of the throughholes, is covered with an insulation layer.
 4. The multilayeredsubstrate for a semiconductor device of claim 3, wherein the metal isaluminum, and the insulation layer covering the entire surface thereofis a layer of alumite (Al₂O₃) obtained by anodizing the aluminumsurface.
 5. The multilayered substrate for a semiconductor device ofclaim 1, wherein the reinforcing sheet joined to the face for externalconnection terminals is in the form of frame.
 6. The multilayeredsubstrate for a semiconductor device of claim 5, wherein the reinforcingsheet has a reinforcing member or members crossing the inside space ofthe frame.
 7. The multilayered substrate for a semiconductor device ofclaim 5, wherein the reinforcing sheet is made of a metal.
 8. Themultilayered substrate for a semiconductor device of claim 6, whereinthe reinforcing sheet is made of a metal.
 9. The multilayered substratefor a semiconductor device of claim 2, wherein the reinforcing sheet isadhered to the face for external connection terminals of themultilayered substrate body by an adhesive.
 10. The multilayeredsubstrate for a semiconductor device of claim 9, wherein the adhesivecontains particles of a diameter that is able to maintain a prescribedgap between the reinforcing sheet and the face for external connectionterminals of the multilayered substrate body such that the adhesive isnot extruded into the through holes of the reinforcing sheet when thereinforcing sheet is joined to the face for external connectionterminals of the multilayered substrate body.
 11. The multilayeredsubstrate for a semiconductor device of claim 1, wherein the reinforcingsheet joined to the face for mounting a semiconductor element thereon isin the form of a frame made of a metal.
 12. The multilayered substratefor a semiconductor device of claim 11, wherein the frame is formed byetching a metal sheet on which the multilayered substrate body is formedso as to remove only the metal material in the region where asemiconductor element is to be mounted.
 13. The multilayered substratefor a semiconductor device of claim 1, wherein the pads provided at theface for mounting a semiconductor device thereon are in the form of bumpso that the tip of the pad protrudes from the face for mounting asemiconductor element of the multilayered substrate body.
 14. Themultilayered substrate for a semiconductor device of claim 2, whereinthe pads provided at the face for mounting a semiconductor devicethereon are in the form of bump so that the tip of the pad protrudesfrom the face for mounting a semiconductor element of the multilayeredsubstrate body.
 15. The multilayered substrate for a semiconductordevice of claim 5, wherein the pads provided at the face for mounting asemiconductor device thereon are in the form of bump so that the tip ofthe pad protrudes from the face for mounting a semiconductor element ofthe multilayered substrate body.
 16. The multilayered substrate for asemiconductor device of claim 11, wherein the pads provided at the facefor mounting a semiconductor device thereon are in the form of bump sothat the tip of the pad protrudes from the face for mounting asemiconductor element of the multilayered substrate body.